ENDOMIXIS 



647 



Vroleptus (Calkins, 1919, 19^0), Euplotes patella (Turner, 1930), and 

 Aspidisca (Summers, 1935), while in others, such as Euplotes worcesteri 

 (Griffin, 1910), "extrusion bodies" are either absent or not described. 

 Again, in some ciliates reorganization bands may not appear so clear-cut 

 as in hypotrichous forms. Nevertheless the macronuclear material is 

 eliminated as a residual mass, left between the two parts of a dividing 

 macronucleus, as in Ancistruma and Concho phthhius (Kidder, 1933a, 

 1933b), Colpidium, Glaucoma, and Urocentrum (Kidder and Diller, 

 1934), and Blepharisma (D. Young, 1939) ; or beside the macronucleus 



Fig. 154. Macronuclear dissolution in Blepharisma undulans. A, vegetative individual 

 with dumb-bell-shaped macronucleus; B, early stage in the formation of the central bulb; 

 C, central bulb fully formed; D, dissipation of the central bulb almost accomplished. 

 (From D.Young, 1939.) 



during or after cell division, as in Chilodonella (MacDougall, 1936) 

 and Colpoda (Kidder and Claff, 1938) (Figs. 153, 154). 



Variations in the details of such intrinsic macronuclear reorganiza- 

 tion processes are indeed legion — reaching their climax, perhaps, in one 

 or more of the types of "hemixis" described by Diller (1936) — but the 

 accumulating data seem to justify the belief that they may be universal 

 in the ciliates and perhaps represent at once a "purification" (Calkins) 

 of the macronucleus, a regulation of the nucleo-cytoplasmic ratio, and 

 a contribution of significance to the metabolic activities of the cyto- 

 plasm. For summaries, reference may be made to Summers (1935) and 

 Kidder and Claff (1938). 



Apparently, intrinsic macronuclear reorganization phenomena dur- 

 ing the division of the cell suffice, in most species at least, for the con- 



